<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <div id="app">
        <input type="text" v-bind:placeholder="tips">

        <hr>
        <div>1+2的结果是：{{1+2}}</div>
    </div>
    <script src="./lib/vue-2.6.12.js"></script>
    <script>
        const mv = new Vue({
            el: '#app',
            data: {
                tips: '请输入用户名'
            }
        })
    </script>
</body>

</html>